KR100267143B1 - Fabrication method of light polarizing particles - Google Patents

Abstract

A method of preparing a polarizer crystal useful for liquid light valve suspension by adding a certain amount of water to the amount of reactant used to prepare the polarizer particles.

Description

Method of manufacturing polarized particles

The present invention relates to improvements in particle production useful for light valve suspensions used to control permeability in light valves.

U.S. Patent Nos. 4,877,313 and 5,002,701 disclose light valves, particles useful for light valve suspensions, and light valve suspensions. In these patents, polarizing materials containing adsorbed iodine include (i) elemental and molecular iodine, (ii) halides of halides or ammonium or alkali metals or alkaline earth metals, and (iii) precursors to precursors and polarizing materials. It consists of a complex salt obtained by reacting in the presence of a polymer stabilizer solution in a non-aqueous solvent that remains insoluble. These particles float in the liquid suspension medium and form a light valve suspension.

The particle size suspended in the light valve suspension is preferably not too large (1 μm or less) to keep the particles suspended without flocculation or settling during repeated on-off cycles of the light valve. Obtaining particles of appropriate colloidal size is unexpected because of the nature and combination of the reaction materials used to form the particles, the various crystallization conditions and variables. Crushing large particles affects the function of particles functioning as light valve particles. Therefore, it is necessary to initially form the particles to a suitable size.

It is an object of the present invention to provide crystals of a polarizing material of a size suitable for use in a light valve suspension.

Another object is to provide a means for forming polarized crystal particles of appropriate size when particles of polarizing material are initially formed.

These and other objects, features and advantages are apparent in the following description.

The present invention relates to the use of (i) elemental, molecular iodine, (ii) halogenated acid or halides of ammonium or alkali metals or earth metals, and (iii) precursor compounds in which the precursor and polarizing materials remain insoluble. Adsorbed iodine containing complex salts formed in the presence of a polymer stabilizer solution in an aqueous solvent and also reacted in the presence of a small amount of water rather than an amount that results in the formation of polarizing material particles having an average particle length of 1 μm or more. It provides a polarizing material.

In general, the present invention includes controlling the particle size of the polarizing material crystals formed from the reaction mixture to provide only small particles suitable to be maintained in the colloidal suspension in the light valve suspension. In the present invention, it was found that the control of the particle size of the crystal can be made by controlling the relative amount of water in the reaction medium used for crystallization of the polarizing material. Excess water in the reaction medium forms large crystals of a size unsuitable for the light valve material, and no light valve particle formation reaction occurs when crystals are formed in the absence of water.

In the present invention, the amount of water to be used for the combined weight of reactants (i), (ii) and (iii) is at most 20% in trace amounts. In either case, the amount of water to be included in the reaction medium can be easily determined experimentally. Generally, the average particle size suitable for light valve particles ranges from 0.2 micron to 1 micron in length, and the greater the amount of water, the larger the particles. It has been found that there is a correlation between the decay time of the light valve suspension containing the particle suspension in the light valve suspension medium and the particle size period in the suspension. Testing for specific particle sizes consists of measuring decay time. The maximum amount of water correlates to a decay time of about 50 milliseconds, which represents 1 micron long particles using the decay time test.

Particle suspension in the light valve suspension medium is charged into a light valve cell of 5 mm spacing glass plates containing appropriate electrodes. The light valve suspension is continuously irradiated with a tungsten lamp. Particle suspension in the light valve is excited by applying 55 volts at 10 KHz to the electrode. It takes 2-3 milliseconds to reach the light valve open state, and after 20 milliseconds the electric field is cut off. The decay time is then measured until the light valve is fully closed. The decay time of 6 milliseconds ("ms") corresponds to an average particle size of up to 0.2 microns, the 20 ms decay time corresponds to an average particle size of 0.7 microns, and the decay time of 50 ms corresponds to an average particle length of more than 1 micron. The decay time is related to the particle size, and the larger the particle, the longer the decay time. Short decay times are preferred. Disintegration times of more than 50 ms indicate inadequate particles that are susceptible to precipitation. Therefore, the maximum moisture content is preferably less than the amount provided by the crystal or particles having a disintegration time of 50 milliseconds or more, depending on the precursor compound. As mentioned above, the maximum moisture content starts at 20% by weight on the basis of reactants (i), (ii) and (iii) by weight.

In the process of the present invention, (i) elemental, molecular iodine, (ii) halides of halides or ammonium, alkali metals or alkaline earth metals, and (iii) precursor compounds are insoluble in which the precursor compound and the polarizing material are insoluble. The reaction is carried out in the presence of an aqueous solvent and a certain amount of water. When the reaction mixture is formed, the precursor compound precipitates at the bottom of the reaction vessel because the precursor compound is insoluble in non-aqueous solvents. The reaction may proceed by contacting the reactants with each other, but it is preferable to increase the reaction rate by stirring the reaction mixture by ultrasonic stirring or the like.

The reaction to form the polarizing material particles is carried out at room temperature with stirring of the reaction mixture and is completed within a few hours. Since the particles of the polarizing material are insoluble in the non-aqueous solvent, the particles are easily separated from the solvent by filtration or centrifugation. Residual non-aqueous solvent can be removed by evaporation.

Precursor (iii) is a metal ion-chelated heterocyclic compound that produces polarized crystals when reacted with elemental iodine (i) and halide (ii). The precursor compound contains a nitrogen atom in the heterocyclic ring and also contains a chelating group. The nitrogen-containing heterocyclic ring contains 4 to 10 members and may contain three additional heteroatoms selected from nitrogen, oxygen or sulfur. The metal ion-chelated heterocyclic compound includes one to four fused heterocyclic rings each having 4 to 10 reducing atoms or a fused hetero ring having 4 to 8 sides. The fused heterocyclic ring preferably has up to four hetero atoms selected from oxygen, nitrogen or sulfur.

For example, the metal ion-chelated heterocyclic compound may have a saturated or unsaturated heterocyclic ring containing at least one chelating group —N (H) —C (CO) — as part of the reducer of the heterocyclic ring. The metal ion-chelated heterocyclic ring may comprise a six-membered aromatic (fully unsaturated) heterocyclic ring having one or more chelating groups —N═C (COOH) — as part of the reducer of the heterocyclic ring.

Compounds (I-V) useful for forming the polarizing material of the present invention include compounds having the following structure:

Wherein R ¹ is carboxy, hydroxy, 2-pyridyl or lower alkyl substituted by carboxy or hydroxy and R ² is carboxy, hydroxy or hydroxy or carboxy substituted lower alkyl. Lower alkyl preferably has 1 to 4 carbon atoms.

Compounds (I-V) are known and dimers, isoforms or analogs of known compounds, and are prepared analogously to known compounds.

2-pyridyl group-containing compounds (I) and (IV) are produced similarly to the preparation of 2,2'-dipyridyl.

Compounds (VI) and (IX) are useful for forming the polarizing material of the present invention.

Wherein R ⁵ , R ⁶ , R ⁷ , R ⁸ are hydrogen or lower alkyl and at least one of R ₅ and R ₆ is lower alkyl.

When R ⁵ , R ⁶ , R ⁷ and R ⁸ are lower alkyl, lower alkyl is straight or branched chain alkyl such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl and analogs. Lower alkyl usually has 1 to 6 carbon atoms. In general, as the carbon number of the lower alkyl substituent increases, the solubility of the compound (VI) or (iii) in the organic solvent increases and the solubility in water decreases. The desired balance of organic solvent / water solubility is obtained by appropriately selecting lower alkyl groups.

Compounds (VI) and (iii) are known and dimers, isoforms or analogs of known compounds, and can be prepared analogously to known compounds.

Preferred precursor compounds are in particular:

Glycine Anhydride (2,5-piperazindione)

5,6-dihydrouracil

Urasol

Succinimide

Glycoruryl (acetylene urea)

Hydantoin

Alanine Anhydride (3,6-dimethyl-2,5-piperazindione)

3-methoxy-2- (1H) pyridone

Quinaldic acid

3,6-dimethyl-pyrazine-2,5-dicarboxylic acid

Pyrazine-2,5-dicarboxylic acid

Pyrazine acid (2-carboxypyrazine)

4-hydroxy quinaldic acid

4-methoxy quinaldic acid

Pyridine-2-carboxylic acid

Picolinic acid

2-hydroxypyridine

Barbituric acid

8-hydroxyquinoline

Cycloleucine

Select from 2,2'-dipyridyl.

The non-aqueous solvent used for forming the particles is a known organic ester such as isopentyl acetate as the liquid suspending medium of the light valve suspension. Preference is given to using hexyl acetate as a non-aqueous solvent. In addition, non-aqueous solvents should be able to dissolve the polymer stabilizer, while precursors and polarizers should be insoluble in non-aqueous solvents.

The halide component of reactant (ii) is usually iodide and may be chloride or bromide.

As described above, a controlled amount of water must be present in the reaction medium for the reaction to proceed. In the absence of water, no reaction occurs, and in the presence of excess water, the particles become too large. In order to determine the amount of water to be used, it is necessary to include water involved in sources such as reactants, polymer stabilizers, non-aqueous solvents. For example, the number of surfaces carried by the precursor compound and the number of crystallites in the precursor compound should be included in the calculation.

The reaction medium also comprises a small amount of methanol in an amount of 5 to 50% by weight of reactants (i), (ii) and (iii) by weight.

Polymeric stabilizers are used to prevent particle agglomeration. Polymeric stabilizers are known to be used to prevent particle agglomeration in light valve suspensions. It is preferable to use nitrocellulose as the polymer stabilizer in forming the polarizing material, and other polymer stabilizers known in the light valve field may be used.

The polarizing material particles become light valve suspensions in a known manner by suspending the particles in a liquid suspending medium, in particular in a mixture with a polymer stabilizer.

In general, the liquid suspending medium may comprise one or more electrically resistant chemically inert liquids that dissolve the polymer stabilizer that suspends the particles and reduces the tendency for particle aggregation to maintain the particles in suspension. Known liquid suspending media can be used (US Pat. No. 4,247,175). In general, one or both of the liquid suspension medium or polymer stabilizer dissolved therein is selected to keep the suspended particles in gravity equilibrium.

The light valve suspension of the present invention is known from US Pat. No. 4,407,565 and is based on the use of an electrically resistive inert low molecular weight liquid fluorocarbon polymer as a liquid medium, wherein the polymer is at least 50% valent halogen atoms and at least 60% halogen fluorine is fluorine. The remainder is chlorine or bromine with a specific gravity of 1.5 at room temperature. Liquid suspension media also include miscible electrically resistive organic liquids, such as trialkyl trimellitates, to provide gravity equilibrium for the suspended particles and to help disperse the particles in the liquid suspension medium. Other materials useful as miscible electrically resistive organic liquids are also known (US Pat. No. 4,772,103). There is also detail on liquid suspension materials (US Pat. No. 4,407,565).

Other types of suspensions that do not contain halogenated liquids are also available, and sufficient amounts of stabilizing polymer can be used to keep the particles in equilibrium.

Another light valve suspension is based on the use as a liquid suspending medium of organic liquids classified as plasticizers. Such “plasticizer” liquid suspension media contain one or more electrically resistive inert organic liquids, which suspend particles and dissolve solid polymer plasticizers. For example, when the solid polymeric plasticizer is a solid poly (meth) acrylate, useful liquid suspending media are adipates, benzoates, glycerol triacetates, isophthalates, melitates, poly (meth) s such as oleates, chloroparaffins, phthalates and sebacates. A liquid plasticizer for acrylate may be included. Liquid suspension media for other solid polymer stabilizers are selected among the liquids useful as plasticizers for these polymers. In particular, trialkyl trimellitates such as tri-n-propyl or tri-n-butyl-trimellitate, dialkyl adipates such as di-octyl adipate or di-2-ethylhexyl adipate may be neopentyl (meth) acrylic. It can be used as a liquid suspending medium for the rate copolymer base polymer stabilizer.

The polymer stabilizer for light valve suspension may be a single polymer that binds to the particle surface and dissolves in the non-aqueous liquid of the suspension medium. Alternatively, there are two or more polymer stabilizers that serve as polymer stabilizer systems. For example, the particles may be a type 1 polymer stabilizer that provides planar coating to the particles, such as nitrocellulose, and also one or more polymer stabilizers that bind to the first stabilizer and dissolve in the suspension medium to disperse the particles and provide steric hindrance to the particles. Can be coated.

Preferably the liquid medium may comprise an A-B type block polymer as a polymer stabilizer to maintain the particles in suspension (U.S. Patent application Serial No. 855,266, filed March 23, 1992, European Patent Publication 350,354). Nitrocellulose or other polymer stabilizers may be provided in the liquid suspension medium in addition to the block polymer. It is preferred to use an A-B block polymer in sufficient amount to keep the particles suspended and the amount used for the light valve suspension is determined experimentally. The polymer stabilizer may be a solid such as a copolymer of neopentyl (meth) acrylate and an unsaturated organic phase or a liquid such as a liquid copolymer of n-butyl acrylate and hydroxyethyl acrylate.

Usually the amount of polymer stabilizer is from 1 to 30%, in particular from 5 to 25% by weight, based on the total amount of liquid light valve suspension. The use of polymer stabilizers, however, is preferred but not necessary in all cases.

The liquid light valve suspension or light valve of the present invention may include commercially available materials such as ultraviolet absorbers, heat stabilizers, non-polymeric surfactants and dispersants.

The liquid light valve suspension may be formed of a film used as a light valve light regulator or used as a light regulator. See, eg, U.S patents and applications (972, 826, 972, 830, November 6,1992).

The following is an embodiment of the present invention.

Example 1

Mix the following ingredients:

40 g of 1/4 sec SS nitrocellulose, dried at 55 ° C. to constant weight, are dissolved in 600 g of hexyl acetate (containing an unknown amount of residual water) and 12 g of the precursor pyrazine-2,5-dicar in this solution. Acid dihydrate (containing surface water) 10.56 g of calcium iodide anhydride, 18 g of iodine element, and 3.5 g of anhydrous ethanol are added. The mixture is shaken for 1 hour during which time polarizing particles are formed as a suspension in hexyl acrylate. The particle disintegration time was 6 milliseconds as measured by the tester.

Example 2

Example 1 is repeated with addition of 0.07 g of water. The decay time of the particles was 9.5 milliseconds.

Example 3

Example 1 is repeated with addition of 0.10 g of water. The decay time of the particles was 15 milliseconds.

Example 4

The ingredients are mixed as follows:

10 g of 1/4 sec SS nitrocellulose, dried at 55 ° C. to a constant weight, is dissolved in 150 g of hexyl acetate (dry through 132 molecular sieves to remove residual water) and 3 g of the precursor compound pyrazine-2,5 -Dicarboxylic acid dihydrate (containing surface water), 2.64 g of anhydrous calcium iodide, 4.5 g of iodine element, 1.10 g of water, and also 3.5 g of anhydrous methanol. The mixture is shaken for 1 hour and then polarized particles are formed in suspension in hexyl acrylate. The particle disintegration time was 6 milliseconds as measured by the tester.

Example 5

Repeat Example 4 with the addition of 0.20 g of water. The decay time of the particles was 8 milliseconds.

Example 6

Repeat Example 4 with the addition of 0.23 g of water. The decay time of the particles was 10 milliseconds.

Example 7

Example 4 is repeated with addition of 0.30 g of water. The decay time of the particles was 11 milliseconds.

Example 8

Example 4 is repeated with addition of 0.35 g of water. The decay time of the particles was 12 milliseconds.

Example 9

Example 4 is repeated with 0.5 g of water and 5 g of anhydrous methanol. The resulting decay time of the polarized particles was 50 milliseconds and the particle size was too large.

As shown in the examples, the disintegration time of the particles (function of particle size) increases with the addition of water. The number of surfaces present in the precursor is variable but generally ranges from 1 to 3% by weight relative to the weight of the precursor. The amount of surface water is determined by drying a certain amount of precursor to a certain weight and subtracting the calculated water present in the crystal water. Crystalline water in the fully hydrated precursor compound is present at a rate of 2 moles of water per mole of precursor. Crystalline water is weakly bound to the precursor compounds, so it is not possible to remove surface water without losing part of the crystallized water.

Claims (7)

precursors selected from (i) elemental and molecular iodine, (ii) halogenated hydrochloric acid, halides of ammonium or alkali metals or alkaline earth metals, and (iii) metal ion chelated heterocyclic compounds containing nitrogen atoms in the heterocyclic ring. In an adsorbed iodine-containing polarizing material comprising a complex salt obtained by reacting a precursor compound and a polarizing material in a non-aqueous solvent in an insoluble state in the presence of a polymer stabilizer solution, Adsorption iodine characterized in that the polarizing material particles are formed in the presence of water in an amount that prevents the formation of polarizing material particles whose average particle length exceeds 1 micron, and wherein the polarizing material particles have an average length of less than 1 micron. Containing polarizing material. The polarizing material according to claim 1, wherein the precursor compound is 2,5-dicarboxypyrazine. A precursor is selected from (i) an elemental molecular iodine, (ii) a halogenated hydrofluoric acid, a halide of an ammonium or an alkali or alkaline earth metal, and (iii) a metal ion chelated heterocyclic compound containing a nitrogen atom in the heterocyclic ring. In the polarizing material particle production method comprising the step of reacting in the presence of a polymer stabilizer solution or a non-aqueous solvent in which the polarizing material is maintained in an insoluble state, Preparation of polarizing material particles, characterized in that the reaction is carried out in the presence of water in an amount that prevents the formation of polarizing material particles but an average particle length of more than 1 micron, and the formed particles have an average length of less than 1 micron Way. 4. A method for producing a polarizing material particle according to claim 3, wherein the precursor compound is 2,5-dicarboxypyrazine. 4. A process according to claim 3, wherein the reaction is carried out in the presence of methanol. 4. A process according to claim 3 wherein the non-aqueous solvent is isopentyl acetate. 4. A process according to claim 3 wherein the amount of water is from traces up to 20% by weight relative to the weight of reactants (i), (ii) and (iii).